Milesg, think you'll find the people burnt by Opes were "sophisticated" investors as Opes FSG said they deal only with sophisticated and institutional investors.
The trouble is sophisticated investors are defined by reference to financial thresholds rather than knowledge and experience dealing with complex legal and financial structures - and a lot of products aimed at sophisticated investors are pretty complex from both points of view (Opes being the perfect example, but there are plenty of others around).
